Commit 0f52d9ed authored by David Makepeace's avatar David Makepeace Committed by Shane Lontis
Browse files

Cleaned up tls1_prf and added comments. 



Reviewed-by: default avatarRichard Levitte <levitte@openssl.org>
Reviewed-by: default avatarShane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8987)
parent e7018588

crypto/kdf/tls1_prf.c

+117 −35
Original line number Diff line number Diff line
@@ -7,6 +7,44 @@ 
 * https://www.openssl.org/source/license.html

 */



/*

 * Refer to "The TLS Protocol Version 1.0" Section 5

 * (https://tools.ietf.org/html/rfc2246#section-5) and

 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5

 * (https://tools.ietf.org/html/rfc5246#section-5).

 *

 * For TLS v1.0 and TLS v1.1 the TLS PRF algorithm is given by:

 *

 *   PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR

 *                              P_SHA-1(S2, label + seed)

 *

 * where P_MD5 and P_SHA-1 are defined by P_<hash>, below, and S1 and S2 are

 * two halves of the secret (with the possibility of one shared byte, in the

 * case where the length of the original secret is odd).  S1 is taken from the

 * first half of the secret, S2 from the second half.

 *

 * For TLS v1.2 the TLS PRF algorithm is given by:

 *

 *   PRF(secret, label, seed) = P_<hash>(secret, label + seed)

 *

 * where hash is SHA-256 for all cipher suites defined in RFC 5246 as well as

 * those published prior to TLS v1.2 while the TLS v1.2 protocol is in effect,

 * unless defined otherwise by the cipher suite.

 *

 * P_<hash> is an expansion function that uses a single hash function to expand

 * a secret and seed into an arbitrary quantity of output:

 *

 *   P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +

 *                            HMAC_<hash>(secret, A(2) + seed) +

 *                            HMAC_<hash>(secret, A(3) + seed) + ...

 *

 * where + indicates concatenation.  P_<hash> can be iterated as many times as

 * is necessary to produce the required quantity of data.

 *

 * A(i) is defined as:

 *     A(0) = seed

 *     A(i) = HMAC_<hash>(secret, A(i-1))

 */

#include <stdio.h>

#include <stdarg.h>

#include <string.h>
@@ -168,25 +206,41 @@ const EVP_KDF tls1_prf_kdf_meth = { 
    kdf_tls1_prf_derive

};



/*

 * Refer to "The TLS Protocol Version 1.0" Section 5

 * (https://tools.ietf.org/html/rfc2246#section-5) and

 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5

 * (https://tools.ietf.org/html/rfc5246#section-5).

 *

 * P_<hash> is an expansion function that uses a single hash function to expand

 * a secret and seed into an arbitrary quantity of output:

 *

 *   P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +

 *                            HMAC_<hash>(secret, A(2) + seed) +

 *                            HMAC_<hash>(secret, A(3) + seed) + ...

 *

 * where + indicates concatenation.  P_<hash> can be iterated as many times as

 * is necessary to produce the required quantity of data.

 *

 * A(i) is defined as:

 *     A(0) = seed

 *     A(i) = HMAC_<hash>(secret, A(i-1))

 */

static int tls1_prf_P_hash(const EVP_MD *md,

                           const unsigned char *sec, size_t sec_len,

                           const unsigned char *seed, size_t seed_len,

                           unsigned char *out, size_t olen)

{

    int chunk;

    EVP_MAC_CTX *ctx = NULL, *ctx_tmp = NULL, *ctx_init = NULL;

    unsigned char A1[EVP_MAX_MD_SIZE];

    size_t A1_len;

    size_t chunk;

    EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL, *ctx_init = NULL;

    unsigned char Ai[EVP_MAX_MD_SIZE];

    size_t Ai_len;

    int ret = 0;



    chunk = EVP_MD_size(md);

    if (!ossl_assert(chunk > 0))

        goto err;



    ctx = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);

    ctx_tmp = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);

    ctx_Ai = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);

    ctx_init = EVP_MAC_CTX_new_id(EVP_MAC_HMAC);

    if (ctx == NULL || ctx_tmp == NULL || ctx_init == NULL)

    if (ctx == NULL || ctx_Ai == NULL || ctx_init == NULL)

        goto err;

    if (EVP_MAC_ctrl(ctx_init, EVP_MAC_CTRL_SET_FLAGS, EVP_MD_CTX_FLAG_NON_FIPS_ALLOW) != 1)

        goto err;
@@ -196,59 +250,85 @@ static int tls1_prf_P_hash(const EVP_MD *md, 
        goto err;

    if (!EVP_MAC_init(ctx_init))

        goto err;

    if (!EVP_MAC_CTX_copy(ctx, ctx_init))

    chunk = EVP_MAC_size(ctx_init);

    if (chunk == 0)

        goto err;

    if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))

    /* A(0) = seed */

    if (!EVP_MAC_CTX_copy(ctx_Ai, ctx_init))

        goto err;

    if (!EVP_MAC_final(ctx, A1, &A1_len))

    if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))

        goto err;



    for (;;) {

        /* Reinit mac contexts */

        /* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */

        if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len))

            goto err;



        /* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */

        if (!EVP_MAC_CTX_copy(ctx, ctx_init))

            goto err;

        if (!EVP_MAC_update(ctx, A1, A1_len))

        if (!EVP_MAC_update(ctx, Ai, Ai_len))

            goto err;

        if (olen > (size_t)chunk && !EVP_MAC_CTX_copy(ctx_tmp, ctx))

        /* save state for calculating next A(i) value */

        if (olen > chunk && !EVP_MAC_CTX_copy(ctx_Ai, ctx))

            goto err;

        if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))

            goto err;



        if (olen > (size_t)chunk) {

            size_t mac_len;

            if (!EVP_MAC_final(ctx, out, &mac_len))

                goto err;

            out += mac_len;

            olen -= mac_len;

            /* calc the next A1 value */

            if (!EVP_MAC_final(ctx_tmp, A1, &A1_len))

                goto err;

        } else {                /* last one */



            if (!EVP_MAC_final(ctx, A1, &A1_len))

        if (olen <= chunk) {

            /* last chunk - use Ai as temp bounce buffer */

            if (!EVP_MAC_final(ctx, Ai, &Ai_len))

                goto err;

            memcpy(out, A1, olen);

            memcpy(out, Ai, olen);

            break;

        }

        if (!EVP_MAC_final(ctx, out, NULL))

            goto err;

        out += chunk;

        olen -= chunk;

    }

    ret = 1;

 err:

    EVP_MAC_CTX_free(ctx);

    EVP_MAC_CTX_free(ctx_tmp);

    EVP_MAC_CTX_free(ctx_Ai);

    EVP_MAC_CTX_free(ctx_init);

    OPENSSL_cleanse(A1, sizeof(A1));

    OPENSSL_cleanse(Ai, sizeof(Ai));

    return ret;

}



/*

 * Refer to "The TLS Protocol Version 1.0" Section 5

 * (https://tools.ietf.org/html/rfc2246#section-5) and

 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5

 * (https://tools.ietf.org/html/rfc5246#section-5).

 *

 * For TLS v1.0 and TLS v1.1:

 *

 *   PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR

 *                              P_SHA-1(S2, label + seed)

 *

 * S1 is taken from the first half of the secret, S2 from the second half.

 *

 *   L_S = length in bytes of secret;

 *   L_S1 = L_S2 = ceil(L_S / 2);

 *

 * For TLS v1.2:

 *

 *   PRF(secret, label, seed) = P_<hash>(secret, label + seed)

 */

static int tls1_prf_alg(const EVP_MD *md,

                        const unsigned char *sec, size_t slen,

                        const unsigned char *seed, size_t seed_len,

                        unsigned char *out, size_t olen)

{

    if (EVP_MD_type(md) == NID_md5_sha1) {

        /* TLS v1.0 and TLS v1.1 */

        size_t i;

        unsigned char *tmp;

        if (!tls1_prf_P_hash(EVP_md5(), sec, slen/2 + (slen & 1),

        /* calc: L_S1 = L_S2 = ceil(L_S / 2) */

        size_t L_S1 = (slen + 1) / 2;

        size_t L_S2 = L_S1;



        if (!tls1_prf_P_hash(EVP_md5(), sec, L_S1,

                             seed, seed_len, out, olen))

            return 0;
@@ -256,7 +336,7 @@ static int tls1_prf_alg(const EVP_MD *md, 
            KDFerr(KDF_F_TLS1_PRF_ALG, ERR_R_MALLOC_FAILURE);

            return 0;

        }

        if (!tls1_prf_P_hash(EVP_sha1(), sec + slen/2, slen/2 + (slen & 1),

        if (!tls1_prf_P_hash(EVP_sha1(), sec + slen - L_S2, L_S2,

                             seed, seed_len, tmp, olen)) {

            OPENSSL_clear_free(tmp, olen);

            return 0;
@@ -266,6 +346,8 @@ static int tls1_prf_alg(const EVP_MD *md, 
        OPENSSL_clear_free(tmp, olen);

        return 1;

    }



    /* TLS v1.2 */

    if (!tls1_prf_P_hash(md, sec, slen, seed, seed_len, out, olen))

        return 0;